Cats are always licking themselves and each other, so when she starts planting kisses on you, it's a good sign. While it's a little different from a romantic kiss that two humans would share, a kitty kiss is still a sign of affection and attachment.
Love and Bonding
Cats lick each other as a form of territorial marking and grooming. One of the first sensations that a cat ever feels is that of her mother cleaning her with her tongue, and as they grow, they learn to groom each other as a form of affectionate bonding. It's like when your partner rubs your feet at the end of a long day -- when your cat gives you kisses, she's claiming you as her own and also demonstrating that she loves you.
You Taste Good
Licking people isn't just a sign of affection -- it can also just be pleasurable for your cat. Some cats can't resist the taste of the natural salts and oils that build up on your skin, while others may be going after flavors left behind from a meal. Even something as simple as your body lotion can smell or taste appealing to your cat, so don't get all sentimental when she starts smooching -- you might just be tasty.
How to Respond
Of course, if you love her smooches and simply want to return the favor, licking her back isn't ideal. In fact, that's probably a little weird for the both of you. Instead, just pet her gently, which can be reminiscent of her mother's cuddles. It feels good for her, she understands that it's an affectionate gesture and you'll get fewer hairballs.
Licking the Issue
If you're a little averse to such moist, ticklish displays of affection, you can gently deter your cat from being so generous with her kisses. Just move her off your lap, and eventually she'll get the idea. You could even dab a little something sour, like lemon juice, onto the areas that she loves to lick as a way of deterring her.
